Abstract

Multisensory integration is thought to require conscious perception. Although previous studies have shown that an
invisible stimulus could be integrated with an audible one, none have demonstrated integration of two subliminal
stimuli of different modalities. Here, pairs of identical or different audiovisual target letters (the sound /b/ with the
written letter “b” or “m,” respectively) were preceded by pairs of masked identical or different audiovisual prime digits
(the sound /6/ with the written digit “6” or “8,” respectively). In three experiments, awareness of the audiovisual digit
primes was manipulated, such that participants were either unaware of the visual digit, the auditory digit, or both.
Priming of the semantic relations between the auditory and visual digits was found in all experiments. Moreover, a
further experiment showed that unconscious multisensory integration was not obtained when participants did not
undergo prior conscious training of the task. This suggests that following conscious learning, unconscious processing
suffices for multisensory integration.